Synthesis of diethyl carbonate by catalytic alcoholysis of urea

The production of diethyl carbonate (DEC) from urea and ethanol was investigated in a batch process. The catalytic activities of many metal oxides were evaluated, the influences of various operation conditions on the DEC yield were explored, and the catalytic mechanism was also analyzed. Among the tested catalysts, ZnO showed the best catalytic activity toward DEC synthesis. The optimum reaction conditions were as follows: ethanol/urea molar ratio of 10, catalyst concentration of 6%, reaction temperature of 463 K, reaction time of 5 h and the reaction pressure of 2.5 MPa, respectively. The highest DEC yield was 14.2%. The reaction of producing N-ethyl ethyl carbamate (N-EEC) was the main side reaction in this process, which consumed both ethyl carbamate and DEC. It is necessary to remove DEC from the reactor as quickly as possible.